32 MECZNIKOW, ON ASCARIS NIGROVENOSA. 
Although the terms “ assistance” and “ co-operation” have 
no definite meaning, no one, probably, would understand 
them as conveying a recognition of perfectly independent dis- 
coveries, no small number of which it has fallen to the author’s 
lot to make. The most important of all the facts adduced by 
Professor Leuckart in the memoir above cited is, beyond 
doubt, the peculiar mode of development of A. nigrovenosa, 
which was discovered by him alone during the autumn vaca- 
tion, when Professor Leuckart himself was no longer at work 
in the laboratory. But not only was the fact of the origin or 
a sexual free larval generation from the embryos of Ascaris dis- 
covered and demonstrated by the author, but the method also 
in which the experimeats must be conducted (consisting in 
the placing of the young larve in moist earth) was determined 
by him quite independently of Professor Leuckart, who had 
recommended him to try various other unsuccessful modes. 
In the anatomical investigation of the various stages of de- 
velopment he owns himself indebted to Professor Leuckart for 
directing his attention to several particulars, and especially 
to the existence of chitinous structures in the second eso- 
phageal enlargement (as before remarked). 
The last stages of the development of A. nigrovenosa in the 
frog’s lung were observed by himself alone. 
Lastly, he ventures to express the hope that the reader, as 
well as Professor Leuckart himself, will not hesitate to recog- 
nise his claim to the discovery. 
